1. Field of the Invention
This invention relates generally to electrostatographic reproduction apparatus which reproduce or copy original document images onto various types of copy sheets. More particularly, this invention relates to such a reproduction apparatus that includes a mechanism for sensing and determining the weight of each type of such copy sheets.
2. Background Art
Electrostatographic reproduction apparatus such as copiers and printers are well known for reproducing or copying original document images onto copy sheets. Typically, each such reproduction apparatus includes one or more sheet supply units from which one type of various types, sizes and weights of sheets is selectable for use in a copying job. After such a selection, sheets are fed seriatim from the selected supply unit by a device, for example a vacuum sheet feeding device, to receive a toner image from an image forming sub-system of the copier or printer. Following such image reception by each copy sheet, the sheet is transported to a fusing station where the toner image is fixed by means of heat and pressure onto the sheet. Thereafter, the sheet is transported to an output section of the copier or printer where such sheets are stacked and, for example, stapled.
The efficiency and overall reliability of such a reproduction apparatus depends in significant part on the performance of its sheet holding, sheet feeding, and sheet transporting devices. In addition, the quality of the copies produced on the copy sheets selected depends significantly on the effectiveness of the heat and pressure fusing station in fixing the toner image onto each such sheet.
Unfortunately, however, the performance of the sheet holding, sheet feeding, and sheet transport devices, as well as that of the fusing station, can be detrimentally affected by changes in the weight of the type of copy sheets selected and subsequently being held, fed, transported, and fused therein. Because there is often a wide range of different types of sheets, for example, the different types and different sizes of copy paper as are well known, such detrimental changes in copy sheet weight tend to occur more frequently than is recognized. For example, sheet multi-feed and sheet misfeed problems at sheet supply units occur in great part because the sheet feeding devices thereof were initially set up optimally for one weight or one type of sheet, but a new and different weight or type of sheet was subsequently added to the supply units without any optimal resetting of their sheet feeding device.